Stop defensively copying AST structures before resolution

pkg/analyzer/lib/src/task/driver.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library analyzer.src.task.driver;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
@@ skipping 649 matching lines @@
         try {
           TaskDescriptor descriptor =
               taskManager.findTask(inputTarget, inputResult);
           return new WorkItem(context, inputTarget, descriptor, inputResult);
         } on AnalysisException catch (exception, stackTrace) {
           this.exception = new CaughtException(exception, stackTrace);
           return null;
         }
       } else {
         builder.currentValue = inputEntry.getValue(inputResult);
+        if (builder.flushOnAccess) {
+          inputEntry.setState(inputResult, CacheState.FLUSHED);
+        }
       }
       if (!builder.moveNext()) {
         inputs = builder.inputValue;
         builder = null;
       }
     }
     return null;
   }
 
   @override
@@ skipping 76 matching lines @@
   final TaskManager taskManager;
 
   _WorkOrderDependencyWalker(this.taskManager, WorkItem startingNode)
       : super(startingNode);
 
   @override
   WorkItem getNextInput(WorkItem node, List<WorkItem> skipInputs) {
     return node.gatherInputs(taskManager, skipInputs);
   }
 }